Alteration of photosystem II activity by atrazine on Chlamydomonas reinhardtii synchronized and asynchronized cell cycle cultures

Inhibition of photosystem II (PSII) activity by atrazine was investigated in the green alga Chlamydomonas reinhardtii during different states of the cell cycle. The algal cultures were maintained under continuous light or under light/dark cycle (16/8?h) to obtain homogenized cell cycle distribution. The cycle state of algal population was determined by the DNA content using flow cytometry and defined as newly divided cells before the initiation of DNA replication (G₀/G₁) and cells at the end of the replication cycle with fully duplicated DNA content (G₂/M). Under different synchronized states of the cell population, the photosynthetic activity was investigated after treatment at 10, 100, and 1000?µmol?L^?1 atrazine exposed for 24?h by using fluorescence parameters related to PSII activity measured with a plant efficiency analyzer and pulse-amplitude modulated methods. In this study, we found that the atrazine effect was different depending on cell cycle phases and the period of illumination. Algal cells under light–dark cycle showed inhibition of the PSII electron transport leading to an increase of heat energy dissipation by the PSII reaction center. Algal cells grown under continuous light was shown to be more resistant to atrazine than the cells grown under light–dark cycle.     

苦草光合作用日变化对水质的影响

通过静态模拟试验研究晴天时苦草(Vallisneria asiatica)的光合作用日变化对水质的影响. 分别采用水下饱和脉冲荧光仪(Diving-PAM)和多参数水质监测仪(YSI)在线监测苦草叶绿素荧光参数与水质,并定时采样测定水中营养盐的浓度. 结果表明,苦草叶片光合作用的相对电子传递速率(rETR)日变化与叶片表面的光合有效辐射(PAR)和温度同步,呈单峰曲线;光系统Ⅱ(PSⅡ)实际量子产量(Y)的日变化呈“W”型;水体的pH和ρ(DO)的日变化与苦草光合作用趋势一致,也呈单峰曲线,而电导率和浊度与光合作用没有相关性;水体中ρ(TN)一直保持稳定,ρ(TP)在23:00时出现峰值.苦草的光合作用能引起水体pH,ρ(DO)和ρ(TP)的改变;且pH和ρ(DO)对底泥磷释放的影响可能是一个动态平衡的过程.      

超旱生植物沙冬青高温胁迫下的快速叶绿素荧光动力学特征

沙冬青Ammopiptanthus mongolicus是温带荒漠地区唯一的常绿阔叶灌木,由于其生长的沙漠中极端高温远高于其它地区,因此研究沙冬青对高温胁迫的响应特征对于解释植物的抗逆机理具有极为重要的意义.快速叶绿素荧光动力学可以在无损情况下探知叶片光合机构的热损伤程度,JIP-test方法将测量值转化为多种具有生物学意义的参数,因而被广泛应用于高温胁迫的有关研究中.对不同环境条件下快速叶绿素荧光诱导动力学曲线的分析可以深入了解植物光合机构对环境的适应机制.本文利用高频采样叶绿素荧光仪在野外下测定了沙冬青在不同温度处理下的荧光响应情况.研究结果表明,沙冬青耐热性在40～45℃;25℃、30℃及40℃时的F_V/F_M在O.80以上,光合反应正常.50℃时出现高温胁迫特征:1)F_V/F_M降低为0.73;2)OJIP曲线变形为OKJIP曲线,K点出现在300 ms左右,值为245.00;3)反应中心的活性下降,Q_A-的还原速率加快.这些变化是由于光合反应中的电子传递受阻引起的,而光合反应中心并没有被破坏,胁迫条件解除后,光合机构还可恢复,说明沙冬青具有极强耐热性.     

CO2倍增对几种植物的生态生理影响

本研究结果表明：木本植物辽东栎、臭椿、丁香叶片气孔对ＣＯ２倍增反应不第三,表现出气孔阻抗不增大,蒸腾速率无明显变化,光合速率比对照增加１０％－２０％或无增加,水分利用效率可提高１０％－１００％不等,叶面积略有增加或接近对照。可以认为ＣＯ２倍增上述植物有不同程度的促进作用,草本植物水稻、大豆、谷子、稗草叶片气孔对ＣＯ２倍增反应敏感,尤其是Ｃ３植物的水稻、大豆、表现为气孔阻抗增大,腾速率减少,光合速率     

稳定塘中氧传递规律研究

在稳定塘污水处理过程中,氧是有机物好氧分解的重要组成部分,稳定塘中氧的来源有藻类光合放氧和大气复氧。本研究通过有光无光对比试验、大气复氧试验及对实际稳定塘中运行数据进行总结研究,定量分析藻类光合产氧和大气复氧量,计算在稳定塘中有机物的总去除量中各部分所占的比例,确定出大气复氧是稳定塘中氧传递的主要方式。      

Effects of soil water and nitrogen availability on photosynthesis and water use efficiency of Robinia pseudoacacia seedlings

The efficient use of water and nitrogen (N) to promote growth and increase yield of fruit trees and crops is well studied.However,little is known about their effects on woody plants growing in arid and semiarid areas with limited water and N availability.To examine the effects of water and N supply on early growth and water use efficiency (WUE) of trees on dry soils,one-year-old seedlings of Robinia pseudoacacia were exposed to three soil water contents (non-limiting,medium drought,and severe drought) as well as to low and high N levels,for four months.Photosynthetic parameters,leaf instantaneous WUE (WUEi) and whole tree WUE (WUEb) were determined.Results showed that,independent of N levels,increasing soil water content enhanced the tree transpiration rate (Tr),stomatal conductance (Gs),intercellular CO2 concentration (Ci),maximum net assimilation rate (Amax),apparent quantum yield (AQY),the range of photosynthetically active radiation (PAR) due to both reduced light compensation point and enhanced light saturation point,and dark respiration rate (Rd),resulting in a higher net photosynthetic rate (Pn) and a significantly increased whole tree biomass.Consequently,WUEi and WUEb were reduced at low N,whereas WUE i was enhanced at high N levels.Irrespective of soil water availability,N supply enhanced Pn in association with an increase of Gs and Ci and a decrease of the stomatal limitation value (Ls),while Tr remained unchanged.Biomass and WUEi increased under non-limiting water conditions and medium drought,as well as WUEb under all water conditions;but under severe drought,WUEi and biomass were not affected by N application.In conclusion,increasing soil water availability improves photosynthetic capacity and biomass accumulation under low and high N levels,but its effects on WUE vary with soil N levels.N supply increased Pn and WUE,but under severe drought,N supply did not enhance WUEi and biomass.     

三种大型海藻对对氯苯胺的去除行为及光合生理响应

以龙须菜、坛紫菜和石莼3种大型海藻为实验材料,通过模拟实验,研究并比较了它们对不同浓度对氯苯胺(PCA)的去除行为,以及石莼对PCA的光合生理响应.实验结果显示,7d实验结束时,3种藻类对海水中PCA的最终去除率排序分别为:6mg·L-1PCA处理组,龙须菜(58.7%)<坛紫菜(75.7%)<石莼(94.9%);60mg·L-1PCA处理组,龙须菜(50.2%)<石莼(61.3%)<坛紫菜(74.9%);海藻的培植密度越大,PCA的去除率越高,在受PCA污染的海域中大面积种植大型海藻来有效地处理修复此类污染在理论上是可行的.在不同浓度PCA处理过程中,石莼的生长受到抑制,有效光化学效率、光合作用和呼吸作用呈现出低浓度(<5mg·L-1)促进、高浓度(>10mg·L-1)抑制的现象.叶绿素、类胡萝卜素和可溶性蛋白含量在各处理组之间没有表现出确定趋势,表明PCA对石莼生长的影响可能是由于呼吸速率的增加而引起的.     

水生生物光合作用对雪玉洞岩溶水体中CDOM的影响

溶解有机质(DOM)作为岩溶水体碳汇的重要组成部分,其来源、分布和迁移变化对研究岩溶碳汇的组成、结构和通量具有重要意义,其组成和结构特征常用有色溶解有机质(CDOM)反演.本研究于旱季每月采集重庆雪玉洞洞内地下水和洞外地表水,通过地下河从洞内向洞外的流动过程中水化学和CDOM光谱特性的变化,分析CDOM的变化影响因素,为研究岩溶水体DOM碳汇通量提供理论基础.结果表明:(1)雪玉洞岩溶水中CDOM以小分子易降解的内源有机质为主,类色氨酸和类酪氨酸组分占60%以上;(2)雪玉洞地下水中的CDOM主要受地下水微生物的降解作用影响,地下水流动过程中有少量易降解有机质被微生物降解,TOC和DOC含量略有降低,CDOM腐殖化程度略有增强;(3)雪玉洞地表水CDOM主要受水池中水生植物光合作用控制,水生植物生长处TOC和DOC含量明显升高,CDOM内源特征和小分子组分明显增多.     

稻草秸秆发酵液的抑藻效应及其机理

为有效利用农业废弃物稻草秸秆进行抑藻,本研究对不同稻草秸秆进行了特定方式的发酵,测定了发酵液对常见淡水藻类的化感效应,探讨了其中抑藻作用强的发酵液抑藻机理.结果表明：与普通稻草秸秆发酵液相比,水稻分蘖枝发酵液对铜绿微囊藻的抑制效果显著好于普通稻草秸秆发酵液（P<0.05）,作用72h水稻分蘖枝发酵液抑制率为93.21%,168h为97.96%,而稻草秸秆发酵液120h抑制率为68.20%,168h抑制率反而显著下降,只有27.65%;前者Eh₅₀为14.073h,后者为21.036h;水稻分蘖枝发酵液对蓝藻（铜绿微囊藻）和绿藻（蛋白核小球藻、斜生栅藻）3种淡水藻均有良好抑制作用,对铜绿微囊藻抑制作用最佳（P<0.05）.在水稻分蘖枝发酵液胁迫下,铜绿微囊藻叶绿素a以及藻蓝蛋白（PC）和别藻蓝蛋白（APC）含量下降,藻细胞叶绿素自发荧光值持续降低,藻细胞结构破坏.推测水稻分蘖枝发酵液的抑藻机制之一是将藻细胞光合系统作为其攻击的靶点从而抑制藻类生长,并最终破坏细胞结构,引起细胞凋亡.     

酸雨对植物光合作用影响的研究进展

随着近年全球酸雨污染程度加重,酸雨对植物的影响受到国内外学者广泛关注。光合作用既是植物生物量和生态系统初级生产量形成的物质基础,也是影响植物生长发育的重要生理过程,因此研究酸雨对植物光合作用影响意义重大。综述了近年有关酸雨对植物叶片形态结构、叶绿体微结构、不同生态型、生活型和不同生育期植物净光合速率的影响,以及不同酸雨组成与复合污染对植物净光合速率影响的相关报道;并从气孔参数、光合色素、叶绿素荧光参数和叶绿体微结构等方面分析酸雨对植物光合作用影响的机制。结果表明:酸雨对植物光合作用器官叶片的影响由外向内递进,由结构向功能延伸;酸雨对植物的胁迫效果存在生态型与生活型差异;在作物不同生育阶段,酸雨对孕穗期影响最为明显;不同成分酸雨对植物影响存在差异,且硝酸型或混合型酸雨对植物的影响大于硫酸型酸雨。